The present invention relates generally to trimmable resistors. More specifically, the invention relates to trimmable resistors for semiconductor devices.
Trimmable resistors may be used with semiconductor devices. Trimmable resistors may be formed on semiconductor device substrates with semiconductor devices. Trimmable resistors allow a trimming that may change the resistance of a resistor after fabrication. Such trimming may be desired when the resistance in a resistor may vary due to manufacturing variations, the needed resistance for the semiconductor device may vary due to manufacturing variations, the needed resistance for the semiconductor device may vary due to the usage of the semiconductor device, or for other reasons.
Laser trimming uses a laser beam to cut electrical connections, which provide for the trimming of a resistor. Generally, such laser trimmable resistors provide a safe area where a laser beam may cut electrical connections. Due to the beam size and beam path, the safe areas may require significant die area to provide an area where only trimmable electrical circuits may be cut by the laser. Such a location should be free of other circuits and should provide sufficient separation between trimmable electrical circuits so that a laser beam only cuts the desired electrical circuits.
Some trimmable resistors may use an applied voltage to metal shorts. Some applied voltage trimmable resistors may require several trim pads, which use die space. Some applied voltage trimmable resistors may require large applied voltages, which may damage semiconductor devices.
Series and parallel switch combinations may also be used to provide trimmable resistors. These series and parallel switch combinations may require extra active circuitry on the die to control the switches. In addition, the trim results may only be valid when the control circuit is powered up.
It is desirable to have a trimmable resistor that requires a minimal amount of chip space and that does not require large voltages.
To achieve the foregoing and other objects and in accordance with the purpose of the present invention, an adjustable resistor between a first terminal and a second terminal is provided. Generally, a plurality of resistors is provided comprising a set of trimmable resistors, where the trimmable resistors are electrically connected together in series and a set of static resistors, where each static resistor is connected in parallel with a trimmable resistor of the set of trimmable resistors. A trim terminal and a plurality of diodes where each diode is electrically connected between a trimmable resistor and a trim terminal are also provided.
These and other features of the present invention will be described in more detail below in the detailed description of the invention and in conjunction with the following figures.